Basic info: www.nationalspanishexam.org
Preparation: https://www.nationalspanishexam.org/index.php/exam-preparation/online-practice-exercises
You may also look on this website under your current level for more resources to prepare for the N.S.E.
Google Sites
Jamboard
Tricider
Hypothes.is
Extempore
Pear Deck / Nearpod
Mindmeister